The present invention relates to ammunition, particularly non-lethal ammunition intended for use in training and war games. More especially, the invention relates to a telescopic cartridge in which rearwards movement of a portion of the cartridge is used to initiate the recycling of an automatic or semi-automatic firearm.
Low energy cartridges for cycling self loading guns are widely known. For example, U.S. Pat. No. 5,677,505 and EP-A-0473758 relate to a two part cartridge which has a casing slidable relative to a plug at the forward end of the cartridge. When the cartridge is fired, force provided by the propellant gas is employed to urge the casing back against the breech-block and recycle the weapon. A cross-sectional view of one embodiment of such a cartridge is illustrated in FIG. 1 of the drawings. The cartridge 2 comprises a cartridge case 4 containing a primer 6 in the base thereof to provide the propulsion energy. A propellant 8 may be contained in the cavity 10 of the case 4 to provide additional energy. A flange 12 is provided at the front end of the case 4. A one piece plug 16 is inserted into the end of the cartridge case 4. The inner diameter 20 of the rear of the plug 16 is equal to the inner diameter of the cartridge case 4. The outer diameter 18 of the front of the plug 16 is equal to the outer diameter of the cartridge case 4. Longitudinal orifices 22 extend from the rear of the plug to the cylindrical recess 24 into which the bullet 26 sits. An inward step 28 is defined between the portions of differing diameter.
On ignition of the primer 6, gas is generated by the primer and/or the propellant. The plug may be restricted in its movement forward by the configuration of the barrel of the gun. Therefore, the cartridge case 4 moves rearwardly along the plug 16 until its movement is restricted by interaction of the flange 12 of the cartridge case 4 with the inward step 28 of the plug 16. Concurrently, the gas flow through the orifices 22 projects the bullet out of the recess 24 and through the barrel of the gun.
The operation of cartridges such as the cartridge shown in FIG. 1 using low energy explosive primers to cycle self loading guns is characterised by using high pressure propellant gas to force the bullet out of the cartridge and through the barrel of the gun at approximately the same time as the gun recycles. However, when the bullet is discharged at the same time as gun recycling, variations in gas pressure and in the orientation of the cartridge components may change the gas flow to the bullet. Thus the bullet is projected from the cartridge case and through the barrel at varying velocities. Moreover, at the same time that the bullet is travelling through the barrel, the recycling action means that the gun components are moving with respect to each other. The combination of variable velocity and gun movements lead to inaccuracies in shooting. When such cartridges are used to fire marking bullets in personnel training, the velocity variations can cause injury when the marking bullet is discharged at too high a velocity.
Alternatively, cartridges have been developed which use high pressure propellant gas to trigger the gun's recycling mechanism before the bullet is ejected from the cartridge and out of the barrel. When the recycling mechanism is operated prior to the discharge of the bullet, the problems mentioned above are accentuated due to the delayed discharge of the bullet.